The present invention relates to a form-adaptable electrode structure in layer construction, e.g., for the contacting of flexible and bendable structures. For example, such structures may be piezoelectric elements in sensor and/or actuator systems.
The use of interdigital electrode structures for contacting electronic components, such as bipolar transistors, surface transducers, piezoelectric sensor-/actuator systems and the like, is conventional. Such a conventional interdigital electrode arrangement is illustrated schematically in FIG. 1. The interdigital electrode structure is usually applied at least on one surface of the electronic component. For protection purposes, generally, a final protective layer is applied on the electrode arrangement, which in turn was applied by vapor deposition or the methods (e.g., laminating, etching) conventional from printed circuit board technology. However, this protective layer cannot be seen in FIG. 1.
Furthermore, European Published Patent Application No. 0 145 033 describes a semiconductor arrangement having an interdigital electrode configuration. In this case, first and second strip-shaped electrodes are applied on a semiconductor arrangement, and in each case are connected to regions of a first and a second conduction type, respectively. So that electrical connections do not squander valuable active regions of the component, the terminal areas necessary for contacting the first and second strip-shaped electrodes situated in one plane, are arranged in a second plane. The second plane is above the plane containing the strip-shaped electrodes. However, such an electrode structure is aimed primarily at reducing the contact terminal areas, in order to waste as little active component area as possible for electrical connections.
The disadvantage of customary interdigital electrodes is that, in response to damage or a crack in a strip-shaped electrode, the flow of current is interrupted, which in turn disturbs the electrical field distribution. This has a negative influence on the functioning of the semiconductor component. Such damage can be formed by cracks and scratches of the metallic electrodes, which in turn can be produced by mechanical stresses in the component, i.e. by bending and deformation of the component.
It is therefore an object of the present invention to provide a reliable electrode structure which is robust, flexible and form-adaptable, in order to ensure the smooth functioning of an electrical component contacted by this electrode structure, even if strip-shaped electrodes of the electrode structure should fail.
The above and other beneficial objects of the present invention are achieved by providing a form-adaptable electrode structure as described herein.
According to one example embodiment of the present invention, the form-adaptable electrode structure is distinguished by a layer construction made of at least two conductor layers, between which an insulating layer is arranged, the conductor layers in each case having first and second electrode strips arranged in parallel, and the electrode strips of the first conductor layer forming an angle with the electrode strips of the second conductor layer, so that a net-like structure is formed. The first electrode strips of the first conductor layer are conductively interconnected with the first electrode strips of the second conductor layer, and the second electrode strips of the first conductor layer are conductively interconnected with the second electrode strips of the second conductor layer by throughplating of the insulating layer at intersections of the net-like structure.
Such an electrode structure built up in layers permits a flow of current despite a failure of electrode strips, and specifically via the plated-through intersections of the insulating layer, so that as an alternative, the conductor tracks on the second conductor layer are used for transporting current. The electrode structure is thus safeguarded. This is particularly necessary when interconnecting or wiring bendable, movable or deformable components, since due to the deformation, the metallic electrode strips generally applied on the component by vapor deposition may get cracks or fractures.
Such an electrode structure may be applied on at least one surface of a base material, first a crack-stopper layer being applied on the surface, then the first conductor layer, followed by the first insulating layer, the second conductor layer and a final further insulating layer.
Such a layer structure may be distinguished by a simple construction which may be produced using customary vapor deposition processes. In addition, by applying a crack-stopper layer between the base material and the first conductor layer, the transfer of cracks to the layer structure is reduced or avoided.
The base material may include a piezoceramic plate, a piezoelectric element, a fibrous composite structure having piezoelectric structures, etc. Generally, the final insulating layer may be used to protect the layer structure.
Furthermore, to generate the field distribution necessary for the sensor suite or actuator suite of piezoelectric ceramic, positive voltage may be applied to the first electrode strips of the first conductor layer and negative voltage to the second electrode strips of the first conductor layer, or the other way around. Positive voltage may be applied to the first electrode strips of the second conductor layer, and negative voltage may be applied to the second electrode strips of the second conductor layer, or vice versa.
According to a further example embodiment of the present invention for generating a desired field distribution in a piezoelectric element, positive voltage is applied to the first electrode strips of the first conductor layer and negative voltage is applied to the second electrode strips of the second conductor layer, or vice versa. In the same manner, the first electrode strips of the second conductor layer may receive positive voltage and the second electrode strips of the first conductor layer may receive negative voltage, or vice versa. That is, the electrode strips may be interconnected as desired depending on the application case. This also implies that the sequence of the interconnection may be arbitrarily selected. That is, first and second electrode strips do not necessarily have to receive voltages of different polarity. Thus, the electrode structure of the present invention is distinguished by an extremely flexible applicability.
Furthermore, the electrode structure of the present invention may have the distinction that the angle between the electrode strips of the first conductor layer and the electrode strips of the second conductor layer is adjustable within a wide range from 0xc2x0 to 180xc2x0. The angle may be, for example, 90xc2x0. However, it may be important that the exact value of the angle is not critical, so that high accuracy is not necessary during manufacturing. This simplifies the manufacturing process and keeps production costs low.
In the following, the invention is explained in greater detail with reference to the attached figures.